Carriage safety system

ABSTRACT

Carriage free fall in catching up with a lowered supporting means is prevented by connecting a chain to a carriage, passing the chain under a fixed lower pulley and then over a fixed upper pulley and connecting the chain to the support. In lift trucks, the support is usually a piston with an idler sprocket over which a chain passes to move the carriage at twice the speed of the piston. The safety chain is passed beneath an idler connected to the piston and is fixed near the upper pulley so that the piston is permitted to move only half the distance of the carriage.

United States Patent [1 1 Smith Jr.

[ 1 Jan. 9, 1973 [54] CARRIAGE SAFETY SYSTEM 2,642,157 6/1953 Milz..107/9 Primary Examiner-Harvey C. Hornsby Assistant Examiner-Merle F.Maffei Attorney-Littlepage, Quaintance, Wray & Aisenberg [57] ABSTRACTCarriage free fall in. catching up with a lowered supporting means isprevented by connecting a chain to a carriage, passing the chain under afixed lower pulley and then over a fixed upper pulley and connecting thechain to the support. In lift trucks, the support is usually a pistonwith an idler sprocket over which a chain passes to move the carriage attwice the speed of the piston. The safety chain is passed beneath anidler connected to the piston and is fixed near the upper pulley so thatthe piston is permitted to move only half the distance of the carriage.

2 Claims, 3 Drawing Figures PATENTEIJJAN 9191a 3.709331 sum 1m 2INVENTOR RAYMOND L. SMITH JR.

ATTORNEYS CARRIAGE SAFETY SYSTEM Many carriage devices which aresupported for upward movement depend upon gravity to insure theirdownward movement as their supporting device is lowered. The verticallymoving carriage of a lift truck is conventionally supported by one ormore chains which are connected to the carriage, pass over pulleys oridler sprockets mounted on the distal ends of vertical pistons and whichchains are fixed at opposite ends with respect to cylinders so that acarriage moves upward at twice the linear speed of the piston.

Lowering of the carriage is effected by controllably releasing pressurefrom the cylinder and lowering the piston, whereupon the carriage movesdownward at twice the speed of the piston. Thus, the carriage dependsupon gravity for its lowering. The control of the speed at which thecarriage is lowered is made by the cylinder and piston, which with thechain, or chains, tend to hold the carriage upward.

A very dangerous condition exists when the carriage is held in anelevated position by some means other than the chain and piston. In thatcondition, when fluid is released from the cylinder with the intentionof lowering the carriage, the weight of the chain and piston cause thelowering of the piston, pulley and chain. The carriage remains in theelevated position supported only by that force which erroneously holdsit. When the force is removed, nothing controls the rate of descent andthe carriage free-falls until it catches up to the chain and piston, oruntil it encounters such obect.

If the carriage is not loaded, and if the distance of free fall is notgreat, and if the carriage is caught by the chain and piston beforeencountering an object, no industrial accident may be recorded, and noinjury or damage may occur.

If the carriage is heavily loaded, if the free-fall distance is great,or if an object is encountered during the free fall, damage may occur tothe load, the surroundings, to the lift truck, and to its mast,cylinder, piston, chain and connections. The lift truck operator, orthose in the immediate surroundings, may be injured.

In many types of lift trucks, particularly in orderpicking warehousestacker-retrievers, the operator rides on the carriage. When thecarriage is operatorridden, the dangers of free fall are magnified.Moreover, even small uncontrolled carriage falls, which do no damage tothe equipment or operator, are extremely disquieting to the operator.

While the cause of a carriage sticking in an unsupported elevatedposition is not important to the consideration of the present invention,several causes might be noted. Dirt may accumulate in tracks along whicha carriage rolls, causing the carriage to stick. Very small articlesfalling between the carriage and tracks may cause the temporary stoppingof the carriage or the slowing of the carriage below the speed ofdescent of the piston. A carriage may come into contact with a fixedexternal object as it is being lowered. When the object moves, thecarriage falls. One potential difficulty might exist in a warehousingsystem in which a truck with an elevated carriage moves in a very narrowaisle. As the carriage was descending, while a truck was moving throughthe aisle a carriage might come into contact with a fixed item such as apallet extending slightly outward from a rack. As the carriage movedbeyond the extended pallet, it would fall before catching up to thepiston and chain which continued descent during the unintentionalhold-up of the carriage. Many causes of malfunction might exist.

While the problem solved by the present invention is particularly acutein the lift truck art, the same problem may exist in any form of stackerretriever, such as a crane or in other forms of movable and fixedelevators. Any support device which is capable of lifting a carriage,but which is incapable of producing a positive downward movement of thecarriage is susceptible to an accident of a type forseen and overcome bythe present invention.

One object of the invention is the provision of carriage controlapparatus for preventing downward movement of a carriage supportingdevice in the absence of corresponding movement of a carriage.

Another object of the invention is the provision of a method forcontrolling the downward descent of a carriage support according to thedownward descent of a carriage.

These and other objects of the invention will be apparent from thedisclosure which includes the foregoing and ongoing specification, theclaims and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an over all view of theinvention as used with a lift truck.

FIG. 2 is a perspective schematic detail of a carriage lifting apparatusof a conventional lift truck.

FIG. 3 is a perspective schematic detail of the carriage safety systemof the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS upper mast extremity l4, and adistal end of the chain is connected to vertically movable carriage 18.

In the warehousing stacker configuration shown in FIG. I, lift truck 10is provided with a rigid vertical mast 20. Mast 20 is connected at lowerextremity to the lift truck and'an upper extremity 22 of mast 20 isconfigured for moving along a horizontal track in a warehouse aisle.Carriage 18 moves vertically along mast 20, and part of the carriage mayfreely roll within the movable section 16 of the main lift truck mastl2. Separate rollers engage the mast 20 and movable section 16.

If carriage 18 becomes stuck in an elevated position, and if pressure isreleased in the cylinder causing mast section 16 to move downward, adangerous condition may exist in which carriage 18 is supported onlybyan obstacle. When the obstacle is removed, carriage 18 may fall untilit catches up with mast portion 16, and its driving piston and thecarriage supporting chain.

To prevent the chain, piston and mast 16 from descending at anatypically high rate with respect'to carriage 18, and to prevent mast l6and its piston and the carriage supporting chain from descending whilecarriage .18 remains stopped, safety apparatus generally referred to bythe numeral 30 is employed. The safety apparatus comprises a chain 32having a first end 34 fixed to an upper portion of mast 20. The flexiblechain 32 is passed under the first rotating means 36 which may be anidler sprocket and which may be generally referred to as a pulley means.Chain 32 then passes over the second rotating means, pulley or idlersprocket 38 which is mounted at upper'extremity 22 of mast 20. Chain 32extends downward under third rotating means 40, which is preferably anidler sprocket and which may be considered as an idler pulley. The chainthen extends upward, and its distal end 42 is connected to carriage 18.

As carriage 18 is forced upward by movement of the piston and thecarriage lifting chain, distal end 42 of chain 32 is pulled upward.Since carriage 18 moves upward at twice the rate of mast portion 16 andidler 36,

the chain is fully taken up by carriage 18. Thus, slack need not existin chain 32. i

For mast section 16 and its associated piston and 'chain idler to belowered, carriage 18 must move .40, 38 and 36, permitting idler 36 tomove downward at half the rate of carriage 18.

As shown in detail in FIG. 2, parallel cylinders 50 drive pistons 52.Distal ends of pistons 52 are fixed to shaft 54. Freely turningsprockets 56 are mounted on opposite. ends of shaft 54. An inner portionof a telescoping mast may also be attached to shaft 54 so that the mastmoves with the shaft. Chains 60 are fixed at ends 62 to-some convenientpoint on the lift truck, such as the cylinders 50. The chains pass overthe first rotating idler sprockets 56, and ends 64 of the chain areconnected to carriage 66. Elements 68 are rollers for moving along amast.

As may be clearly seen from the drawings, when carriage 66 remains in anelevated position after pressure is relieved from cylinders 50, pistons52, shaft 54, sprockets 56 and chain 60 fall, carriage 66 is left in aprecarious position in which it is ready for free fall. To preventcarriage free fall, the apparatus shown in FIG. 3 is employed. As alsoshown in FIG. 1, end 42 of chain 32 is'connected to the carriage. Theopposite end 34 of chain 32 is fixed at a point above the carriage.

-Chain 32 extends below idler sprocket 36 which is mounted on shaft 54as shown in FIG. 2. The chain then extends over the second idlersprocket 38 and under the third idler sprocket 40. In the lattercondition, shaft 54 and hence, idler sprockets 56 and the carriagesupporting chain and the shaft attached pistons may not move downwarduntil downward movement of the carriage permits chain end 42 to movedownward, thus, moving chain 32 and permitting idler 36 on shaft 54 tomove downward. Because theidler sprocket 36 and idler sprockets 56 aremounted on the identical shaft 54, the idler sprockets 36 and 56 onshaft 54 are generally referred to herein as the first rotating means ormovable pulley means.

While the invention has been particularlydescribed for use with lifttruck apparatus, the invention which is embodied in FIG. 3 may be usefulin any form ofcarri e which i confi ur d for u and own ovement.

hile the inventi on has beeh parti cular y shown and described withreference to a preferred embodiment thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spiritand scope of theinvention.

What is claimed is:

l. Carriage safety apparatus comprising'mast means for supporting loads,carriage means mounted on the mast means for up and down movementthereon, extensible means mounted adjacent the mast means for moving thecarriage means upward on the mast means, first rotating means mounted onthe extensible support means for movement therewith,second and thirdrotating means mounted on the mast means respectively near upper andlower extremities thereof, a first flexible means fixed with respect tothe mast means near a lower portion thereof, extending over the firstrotating means and connected to the carriage means for lifting thecarriage means with upward movement of the extensible means and firstrotating means, and second flexible means attached to the carriagemeans, the second flexible means passing sequentially under the thirdrotating means, over the second rotating means, and under the firstrotating means, and being fixed to the mast means at an upper portionthereof for preventing downward movement of the first rotating means andextensible means in the absence of downward movement of the carriagemeans.

2. The apparatus of claim 1 further comprising a I vehicle, and whereinthe mast means comprises a first

1. Carriage safety apparatus comprising mast means for supporting loads,carriage means mounted on the mast means for up and down movementthereon, extensible means mounted adjacent the mast means for moving thecarriage means upward on the mast means, first rotating means mounted onthe extensible support means for movement therewith, second and thirdrotating means mounted on the mast means respectively near upper andlower extremities thereof, a first flexible means fixed with respect tothe mast means near a lower portion thereof, extending over the firstrotating means and connected to the carriage means for lifting thecarriage means with upward movement of the extensible means and firstrotating means, and second flexible means attached to the carriagemeans, the second flexible means paSsing sequentially under the thirdrotating means, over the second rotating means, and under the firstrotating means, and being fixed to the mast means at an upper portionthereof for preventing downward movement of the first rotating means andextensible means in the absence of downward movement of the carriagemeans.
 2. The apparatus of claim 1 further comprising a vehicle, andwherein the mast means comprises a first rigid mast mounted on thevehicle, wherein the extensible means comprises a second extensible mastmounted on the vehicle and wherein the carriage means comprises amaterials handling carriage mounted on the first mast for verticalmovement therealong.